1. Field of the Invention
Exemplary embodiments of the present invention generally relate to an image forming apparatus and an image forming method capable of controlling position of the image at the time of forming image of a plurality of colors.
2. Discussion of the Background
In a background color image forming apparatus, the color image is formed by piling up images of a plurality of key colors. If the image position of each key color shifts, the color of a line drawing or a character can change, or image unevenness (uneven coloring) can occur, and the image quality can be decreased. Therefore, it is necessary to ensure that the image position of each key color is accurate.
A background color image forming apparatus compensates for the displacement between the key colors generated according to various factors, such as change of environmental temperature and change of inside temperature.
For example, a background color image forming apparatus compensates for the displacement by detecting the inclination of a pattern for compensation formed on a transfer belt.
However, in a background color image forming apparatus, since there are many patterns for compensation formed on a transfer belt and detected by one sensor, it can take a long time for the compensation to be completed. Thus, it is desirable to reduce waiting time for a user, and it is desirable to reduce the decline of the average print speed.
In a background color image forming apparatus, during sequential printing, the apparatus forms the patterns for compensation on the transfer belt and compensates for any image displacement. It is necessary to form the patterns between print images (between sheets). Therefore, the domain of forming patterns is restricted. Extending the domain between sheets results in a large area for many pattern formations, but the print speed may be reduced.